Afterburner shroud construction



Aug. 12, 1958 E. D. BROWN AFTERBURNER SHROUD CONSTRUCTION Filed Oct. 25, 1952 N /NVENTOR EDMUND D. BROWN United States Patent() 2,846,842 v AFTERBURNER sHRoUD coNsTRUc'rIoN Edmund D. Brown, Manchester, Conn., assignor to United Aircraft Corporation, East Hartfordz Conn., a corporation of Delaware Application October 25, 1952, Serial No. 316,920

z Claims. (Cl. so- 356) This invention relates to improvements in a shroud construction and has particular reference to a pressurized shroud, which while not limited thereto, is particularly adapted to an afterburner of ajet engine.

An object of this invention is to maintain control of the radial clearance between the inner shell and the outer shell of a shroud.

Another object of this invention is to provide a pressurized shroud construction which will permit an afterburner of a jet engine to operate at a high temperature.

A further object of this invention is to provide a shroud construction which will permit relative axial movement between the inner and outer shell thereof.

Other objects and advantages will become apparent from the following description.

In the accompanying drawings there is illustrated a suitable mechanical embodiment for the purpose of disclosing the invention. The drawings, however, are for the purpose of illustration only and are not to be taken as limiting or restricting the invention. It will be apparent to those skilled in the art that various changes in the illustrated construction may be made without exceeding the scope of the invention.

Fig. l is a view in elevation of a jet engine and afterburner showing part of the cooling system.

Fig. 2 is an enlarged view of a section of the afterburner partially in longitudinal section showing the construction of the pressurized cooling shroud.

Fig. 3 is an enlarged longitudinal sectional view of the pressurized cooling shroud showing the forward support, the rearward support and the connection of the compressed air pipes with the shroud.

Fig. 1 shows a jet engine 2 having an air inlet 4, a compressor section 6, burner section 8, turbine section 10, and having an afterburner 12 and nozzle 14 attached thereto, The nozzle shown in these figures is shown and claimed in U. S. Patent No. 2,831,319. While a particular nozzle has been shown in these llgures, it is to be understood that any type nozzle desired may be used.

The afterburner 12 includes a diffuser section 16 and a burner section 18. These two sections, 16 and 18, are attached together by means of a flange 20 on thedifuser section 16 and a ilange y22 on the burner section 18. These flanges are held together as by bolts 24. The nozzle 14 is attached to the afterburner 12 and is actuated by pistons in cylinders 26. An actuating fluid is directed to said cylinders in a manner to be hereinafter described.

As seen in Figs. 2 and 3 the burner section 18 of the afterburner is constructed having two shells, an inner shell 28 and an outer shell, or shroud, 30. The outer shell 34) is connected at its forward end to the diffuser section 16 of the afterburner by the llanges 20 and 22 and bolts 24 as above described. The forward end of the inner shell 28 is allowed to lloat between the forward end of the outer shell and a substantially cylindrical ring 32 whichY is secured in place by an integral disc ange or llat ring 34 which is held between the llanges 20 and 22.

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The ring or cylinder 32 is spaced radially inward from the outer shell as shown. This forward mounting arrangement permits the inner shell to expand both longitudinally and radially without adverse effect on associated parts. The rearward ends of the inner and outer shells are connected by a plurality of mounting devices 36. These devices permit relative radial movement between the two shells, 28 and 30.

These devices include two units. One unit is xed in relation to the inner shell and the other unit is fixed in relation to the outer shell. The unit fixed to the outer shell consists of a spacer 38 and bushing 40 which has a circular flange 42 attached thereto. The bushing fits into a hole 41 in the outer shell and the spacer 38 and flange 42 are attached to the outer shell around said hole by any means desired. The unit llxed to the inner shell includes a bolt 44 which extends through a hole 46 in said inner shell and has a head tapered at 48 to t in a tapered part 50 of the hole 46. A sleeve 52 is placed with its inner diameter around said bolt and with its outer diameter engaging the inner diameter of bearing 40 in a manner to permit sliding motion therebetween, the length of the sleeve 52 being longer than that of the bearing 40. A washer 54 is placed over the threaded free end of the bolt 44 against the end of sleeve 52. A nut 56 is then placed on the threaded free end of the bolt 44 and positioned so as to llxedly mount this unit to the inner shell 28. As it can now be seen, relative radial movement is permitted between the inner shell and the outer shell, or shroud, 30 by an amount equal to the dillerence in length between the sleeve 52 and the bearing 40. These devices prevent axial movement between inner and outer sleeves at this point as will be apparent.

Compressed air is introduced into the space between the inner shell 28 and outer shell, or shroud, 30 through a piping system 58. This system as shown includes a pipe 60 connected to the compressor of the engine in such a manner that compressed air can be fed into it, a pressure valve 62 for controlling the admission of the compressed air which operates in a manner to be later herein described, and a Y section of pipe which permits a header 66 to extend down on either side of the engine (only one side being shown in Fig. l). Each header has three connections 68 which are connected by pipes 70 to pipe sections 72 which are in turn connected to the outer shell, or shroud, 30 by a flared out section. These sections are flared to insure a smooth llow of air into the area to be pressurized and also to insure that the pressurized air will be introduced through a greater degree of arc to assist in circumferential distribution of the pressure. Sufcient pressure is introduced into the area between the shells at 74 so that the combustible gas at 76 will not llow through the forward mounting arrangement ofthe inner shell 28. While the source of the compressed air is shown as the compressor of the engine, it is to be understood that the air may be supplied from any means desired. It is also to be understood that other types of cooling lluids besides air may be used.

Downstream from the points at which the air is introduced into the area between the inner and outer shells a circumferential restriction 78 is placed to further aid in equalizing the pressure of the air around the entire circumference of the volume between the inner and outer shells 28 and 30. This restriction is formed by a rigid circumferential member 80, a flexible circumferential seal member 82 and a plurality of spacers 84. These three parts of the restriction are fixed to the outer shellby-a plurality of bolts 86 spaced therearound.

The rigid circumferential member is formed having a flat circular part 88 and a frustro-conical part'90. The free edge of the fruStro-conical part of this member 80 is spaced from the inner shell 28. This spacing permits expansion of the inner shell in relation to the member. To restrict the annular opening 81 formed between the member 80 and the inner shell 28 a flexible circumferential seal member is used. This seal member 82 is formed from two members each having a fiat circular part 92 and a frustro-conical part 94. The frustro-conical portion of each member is segmented and the segments of one frustr'o-conical section cover the meeting edges of the segments of the otherfrustro-conical section. This arrangement provides a leaf spring action which restricts the annular opening 81 formed between the member 8f) and the inner shell 28 as the inner shell and outer shell move in relation to one another. Each bolt 86 referred to above extends from the outer shell through a spacer 84, a hole in the fiat annular part 92 of the seal member 82 and a hole in the flat annular part 88 of the rigid member 80. The height of the spacer 84 determines the size of the restricted opening.

From the restriction 78 to the end of shell, or shroud, 30 the annular space between the inner shell 28 and outer shell, or shroud, 30 is gradually decreased. At the end of the outer shell, or shroud, 30 a ring 96 and a ilexible circumferential seal member 98 are mounted. Ring 96 is mounted to the outer shell, or shroud, 30 by means of a ange 100 on said outer shell and a flange 102 on said ring. Bolts 104 secure one flange to the other. The free end of ring 96 has a frustro-conical section 106 with a flared portion 108. This ared portion 108 is spaced from the free end of the inner shell 28. The dimension of this space is such that when the nozzle 14 is open and the after-burner is on the free end of the inner shell will be approximately just in meeting contact with it. A ring of this type lis shown and claimed in U. S. Patent No. 2,735,262. Holes 110 are provided in the frustroconical section 106 of ring 96 to permit the air to flow through said outer shell, or shroud, 30.

Seal member 98 is also mounted on the outer shell 30. Aange 112 on said member is secured to ange 100 by bolts 104. The free end of said seal member contacts a. member 117 of the nozzle 14 to prevent a leak at this point when the nozzle is in a closed position.

It s desired to have air owing through the piping system 58'and between the inner 4and outer shells 28 and 30 when the afterburner is on and the nozzle 14 is openf Conversely, it is desired that no air be flowing through the piping system 58 and between the inner and outer shells 28 and 30 when the after-burner is olf and the nozzle 14 is closed since at this operating condition there is no need for this action.

While the above operation can be performed manually by having a manually controlled valve in place of pressure valve 62 and making nozzle 14 a manually operable nozzle, it is preferred that an automatic control be used. An automatic control of a type which could be used is shown and claimed in U. S. Patent No. 2,715,311. This control senses when the afterburner goes on or oth and opens or closes the nozzle accordingly and maintains it in that position. When the afterburner is on this nozzle and valve actuator control 115 permits an actuating iiuid to be directed by conduit 262 to manifold 116 and in turn delivered to the rearward ends of cylinders 26 by conduit sections 118. This connection holds nozzle 14 open When the `afterburner is olf this nozzle and valve actuator control 115 permits an actuating fluid to be directed by conduit 266 to manifold 120 and in turn delivered to the forward ends of cylinders 26 by conduit sections 122. This connection holds nozzle 14 closed Pressure valve 62, which regulates the `'admission of compressed air to the space between the inner and outer shells may be of several types depending on how it is connected to the nozzle and shroud actuator control. One type is a pressure valve which is normally closed and arranged to open when subjected to a predetermined pressure. This valve can then be connected to conduit 262 by conduit 124 and the proper operation of both the cooling system and nozzle would be obtained.

When the afterburner is turned on, the nozzle and valve actuator control connects conduit 262 to an actuating fluid and connects conduit 266 to drain. This actuates pressure valve 62 through conduit 124 in an opening direction and nozzle 14 through manifold 116 and conduits 118 in an open direction. When the afterburner is turned olf, the nozzle and valve actuator control 115 connects conduit 266 to an actuating fluid and connects conduit 262 to drain. This actuates pressure valve 62 in a closing direction and nozzle 14 through manifold 120l and conduit 122 in a closing direction.

Although a speciiic shroud construction has been shown and described herein for the purpose of illustration, it will be evident to those skilled in the art that the invention is capable of various modifications and adaptations within the scope of the appended claims. The pressurizing system as shown in this application is shown and claimed in the copending application of Donald l. Jordan, Serial No. 316,905, filed October 25, 1952, for a Pressurized Afterburner Cooling Shroud.

I claim:

l. A jet engine having a compressor, a turbine, a burner located therebetween and an afterburner, said afterburner having a unitary inner shell of circular cross section and an outer shell of circular cross section and concentric with, spaced from and enveloping said inner shell to deline an annular liow passage therebetween, the forward end of the outer shell being fixedly mounted to said engine, an axially extending cylindrical member spaced radially inward from and connected to said outer shell and extending axially rearwardly to form a rearwardly opening annular space with said outer shell, the front end of said inner shell being located in said space and having radial clearance with respect to the outer shell and said member, said front end of said inner shell and said member being constructed and arranged so that said front end will remain in said space during any relative movement between the twoshells, means for mounting the rearward ends of said shells to permit radial movement therebetween While restraining axial movement therebetween including a plurality of radially extending and circumferentially spacedl pins Iixed to said inner shell and passing in slidable engagement through a plurality of bushings fixed in said outer shell, duct means attached to the rearward end of said outer shell and extending rearwardly therefrom and terminating radially outwardly of said inner shell rearward end and spaced therefrom to restrict flow at the exit of said ow passage and to contact said inner shell rearward end to support same when said inner shell expands, and means in said duct means to permit metered liow through said passage when said inner shell rearward end and said duct means Contact.

2. A jet engine having a compressor, a turbine, a burner located therebetween and an -afterburner, said afterburner having -a unitary inner shell `of circular cross section and defining the combustion zone of said afterburner and culminating in a rearward end which defines an exhaust gas outlet for said engine and an outer shell of circular cross section and concentric with, spaced from and enveloping said inner shell to define an annular flow passage therebetween, the forward end of the outer shell being xedly mounted to said engine, said outer shell being formed of at least two parts, a first part having a flange extending radially outwardly from its forward periphery, a second part having a larger diameter than said first part and having a ange extending radially outwardly from its rearward periphery, said last two flanges being iixedly mounted one in relation to the other, a -liange member being tixedly held in sealed relation between said two flanges and supporting an axially rearwardly extending annular ring of circular cross section and of substantially the same diameter as said first part and positioned in spaced radial relation -toand within .said outer shell to form a rearwardly opening annular space therewith, the front circular portion of said inner shell being located in said space with radial clearance between said member, said outer shell and said inner shell, said front end of said inner shell and said member being constructed and arranged so that said front end will remain in said space during any relative movement between the two shells, means for mounting the rearward ends of said shells in a manner to prevent axial relative movement and to permit radial relative movement therebetween, said last named means including a plurality of circumferentially spaced mounting devices, each mounting device comprising a pin type member fixed to and projecting radially outwardly from said inner shell and a bushing type member xed to said outer shell and receiving said rst member in sliding engagement, ow restricting means comprising a duct member of circular cross section attached to the rearward end of said outer shell and extending rearwardly therefrom while converging toward said inner shell and culminating in a rearward end which is positioned radially outwardly of said inner shell rearward end to define a first outlet for said annular flow passage therewith and spaced radially therefrom so that when said inner shell expands due to afterburner operation at elevated temperatures said ow restricting means rearward end contacts and supports said inner shell rearward end in concentricity, and said flow restricting member having a plurality of `circurnferentially spaced holes therein to deiine a second outlet for said annular ow passage to permit metered flow through said annular ilow passage when said inner shell rearward end and said flow restricting means rearward end contact.

References Cited in the le of this patent UNITED STATES PATENTS 2,508,420 Redding May 23, 1950 2,603,060 Brown July 15, 1952 2,616,662 Mierley Nov. 4, 1952 2,625,793 Mierley et al. Jan. 20, 1953 2,630,673 Woll Mar. 10, 1953 2,631,796 Williamson et al. Mar. 17, 1953 2,699,040 Gaubatz Jan. l1, 1955 2,702,454 Brown Feb. 22, 1955 2,722,801 Lombard Nov. 8, 1955 

